/Engine/Plugins/Online/OnlineSubsystemUtils/Source/OnlineSubsystemUtils/Classes/OnlineSessionClient.h
Called from GameInstance when the user accepts an invite
virtual void OnSessionUserInviteAccepted ( const bool bWasSuccess, const int32 ControllerId, FUniqueNetIdPtr UserId, const [FOnlineSessionSearchResult](API\Plugins\OnlineSubsystem\FOnlineSessionSearchResult) & InviteResult )